BEIJING — The blasts that killed 165 people at one of China’s busiest seaports last year were a result of a culture of mismanagement at a chemical warehouse and lax oversight by regulators, according to a government investigation whose results were released Friday.

In the report, officials with the State Council, China’s cabinet, described the explosions in Tianjin six months ago as a man-made disaster that had caused $1.1 billion in damage, destroying more than 300 buildings and injuring nearly 800 people, according to Xinhua, the state news agency.

Officials vowed to punish 123 government workers in connection with the blasts, citing dereliction of duty. Another 49 people have already been placed under investigation, many of them employees of Rui Hai International Logistics, which operated the warehouse at the center of the blasts.

The explosions, one of the worst industrial disasters in Chinese history, prompted unusually impassioned calls for action from the Communist Party. Many people pointed to the disaster as a watershed moment, saying it had exposed the high cost for Chinese society of rapid industrialization.

Ma Jun, a prominent environmentalist, said Friday that the investigation underscored the need to improve communication among government departments and to crack down on companies that violated safety rules.

“This was by no means, at all, a natural disaster,” Mr. Ma said. “It was caused by human error: one error after another, one failure after another.”

Greenpeace called for an overhaul of China’s chemical management system, saying in a statement on Friday, “Tianjin should be the catalyst for this.”

The report said the explosions had occurred when an improperly stored chemical became too dry and ignited, setting fire to nearby containers full of explosive substances. The chemical, nitrocellulose, is used in nail polish and lacquer. It was near containers of ammonium nitrate, a highly explosive chemical commonly used in fertilizers.

Officials said that Rui Hai had committed a series of safety violations, including illegally building a freight yard, illegally storing hazardous materials and showing “inept safety management.”

Rui Hai was storing more than 11,000 tons of hazardous goods at its warehouse before the disaster, including more than 200 tons of nitrocellulose and 800 tons of ammonium nitrate, far in excess of what was allowed, the investigation found. Rui Hai’s license will be revoked, and its executives will be banned from working in the chemical industry, the report said.

The blasts in Tianjin turned a flourishing economic zone into an apocalyptic scene overnight. The report said that more than 12,400 cars had been damaged, as well as more than 7,500 shipping containers.

While the blasts brought severe pollution to nearby waterways and soil, the report said that there appeared to be no lasting damage to the Bohai Sea.

Zhang Tiantian contributed research from Beijing.

A version of this article appears in print on , Section A, Page 9 of the New York edition with the headline: China Vows to Punish Managers for Inferno. Order Reprints | Today’s Paper | Subscribe